Run flat device

ABSTRACT

An annular ring-shaped run flat device is used in tires to permit continued use of the tire even when the tire is operating at low pressure or is completely deflated. This device is comprised of a rigid section and a non-rigid section. The tire, when it collapses, due to a reduction in pressure, comes to rest on the surface of the non-rigid, resilient, impact resistant section. This device is easy to assemble, can be used with conventional multi-piece rims, is light weight, durable and capable of absorbing impact under both inflated and deflated conditions. The device can also be used as a positive and non-positive bead spacer to prevent dismounting of the tire beads when tire pressure drops.

This is a continuation of application Ser. No. 507,836 filed on June 23,1983, now abandoned.

The foregoing abstract is not to be taken as limiting the invention ofthis application, and in order to understand the full nature and extentof the technical disclosure of this application, reference must be madeto the accompanying drawings and the following detailed description.

BACKGROND OF THE INVENTION

The present invention relates to a new type of run flat device forpneumatic vehicle tires.

Various run flat devices exist for pneumatic vehicle tires. Theirgeneral purpose is to provide a surface on which the inner surface ofthe portion of the tire beneath the tread can rest when air is purposelyor accidentally removed either totally or to a great degree such thatthe pneumatic tire collapses totally or partially. The tire then can berun on the vehicle for a period of time until the vehicle operator isable to replace it with another tire. Such deflations could occur on apassenger tire on a street or highway, on an off-the-road vehicle thatwould come in contact with sharp and abrasive objects, and militaryvehicles whose tires might be punctured by a bullet or shrapnel.

Many prior art devices have been inadequate because they were not strongenough to support a vehicle with a deflated tire or absorb impact whenthe tire was inflated, but came into contact with an irregular surfacesuch as a chuck hole or a log, which would cause the inner surface ofthe tire, even though completely inflated, to come in contact with therun flat device. Other devices were not easy to assemble or requirednonconventional rims.

There has therefore been a need for a highly durable, light weight,impact resistant, heat resistant run flat device which was easy toassemble and which could be used on conventional rims.

An object of an aspect of this invention is to provide a light weight,run flat device which can be used with conventional rims and is easy toassemble. An object of an aspect of this invention is to provide adurable run flat device which will absorb impact under inflated anduninflated conditions. An object of an aspect of this invention is toprovide a run flat device which is relatively heat resistant. An objectof an aspect of this invention is to provide a run flat device which isalso a bead spacer.

In accordance with one aspect of this invention there is provided anannular ring shaped, run flat device comprising a radially outer ringwhich is non-rigid and flexible and a radially inner ring which isrigid. The outer ring provides the resilient load bearing surface whilethe inner ring is the load carrying member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a two-piece device with both piecesfastened together.

FIG. 2 is a cross sectional view of the device mounted on a three-piecerim.

FIG. 3 is an enlarged side view of a portion of the device positioned ona rim inside a tire.

FIG. 4 is the cross sectional view of another embodiment of the device.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment of the present invention, the rigid non-flexibleradially inner ring has a cross-section with an outer shape that can berectangular or trapezoidal.

The radially inner ring is substantially hollow so as to contribute tothe light weight of the device. While the radially inner ring issubstantially hollow, it can contain radial reinforcements. These radialreinforcements should be used sparingly so as to keep the weight of thedevice to a minimum. To further reduce the weight of the device openingscan be present in the top side and/or lateral sides and/or bottom sideof the radially inner ring. The number and size of the openings arelimited only by the structural strength requirements of the device,i.e., to absorb the impacts experienced by the device either while thetire is inflated or under reduced or zero pressure.

The hollow radially inner ring need not possess a bottom side. When itdoes not, it can be attached to the wheel rim through the bottom edgesof its lateral sides, or radial reinforcements, if present, or in anyother desired manner.

The resilient non-rigid radially outer ring also has a rectangular ortrapezoidal cross-section. Its radially inner surface should be no widerthan the radially outer surface of the rigid ring. Preferably it is thesame width.

In one embodiment both the rigid and non-rigid rings have rectangularcross sections with the top side of the rigid portion being essestiallythe same width as the bottom side of the non-rigid portion. In anotherembodiment, both rings have trapezoidal cross sections with the widebases being radially inward and the outer side of the rigid portionbeing essentially the same width as and centered on the inner side ofthe non-rigid portion.

The outer ring can rely solely on the inherent resiliency of thematerial of which it is comprised for its overall resiliency andflexibility. However, it can also rely on its shape to enhance itsresiliency and flexibility, e.g., by openings within the body thereof orgrooving in its radially outer surface.

For larger vehicles the radially outer surface of the non-rigid ringshould contain less grooving and preferably no grooving at all. Thenon-rigid ring should also be of a lesser thickness for heavy vehicles.When used with lighter vehicles, the thickness and/or grooving can beincreased, if desired.

The outer surface of the non-rigid portion should be relatively flat orslightly rounded to more uniformly distribute the load over the contactarea.

In one embodiment, particularly where the device is used for a heavyvehicle, the radially outer ring has a rectangular cross section and acontinuous, flat outer surface and the radially inner ring has arectangular cross section and an opening therein which is essentiallyrectangular in shape. Preferably the inner ring has no bottom side. Theradially inner ring would therefore have a squared U, i.e., squaredhorseshoe shape such as depicted in FIG. 2.

The use of a flexible, resilient component having the load bearingsurface, with a rigid load carrying member beneath it, results in asatisfactory run flat device.

In one embodiment, the total section height of the run flat device fromthe rim base to the outer surface 8 of the resilient outer ring is 25 to55 percent, preferably 30 to 45 percent of the total section height ofthe tire in which it is positioned, the section height of the tire beingone-half times the difference between the outer diameter of the tire andthe nominal rim diameter. The total section height of the run flatdevice varies according to the loading requirements of the vehicle andtire and the type of service. For example, the total section height ofthe run flat device should preferably be 30 to 45 percent of the tiresection height for large all terrain military vehicles, most preferably30 to 35 percent.

The rigid device may be made of any rigid material including metals.Examples of metals are steel, magnesium and aluminum. It can also bemade from rigid plastics such as fiber reinforced composites. Magnesiumand aluminum are particularly desirable because of their light weight.Plastic materials should be selected carefully with consideration beinggiven to their high temperature properties, since heat build-up canoccur during the use of this device. The top side and lateral sides ofthe rigid device as well as any supports can be and preferably are of aunit construction, but can be separate components.

The entire device itself must be in at least two parts so as to becapable of being placed inside the tire. In this respect see 2 and 2' inFIG. 1.

The non-rigid portion can be any material which will deflect upon impactbut return to its original configuration when the impact is removed.Vulcanized elastomers are preferred materials, both natural andsynthetic.

The bottom surface of the non-rigid outer ring and radially outersurface of the rigid inner ring can be positioned against one another inany conventional manner, for example by fasteners or conventionalmetal-to-rubber adhesives or by having interlocking surfaces, so long asthe two rings are rendered incapable of relative movement in anydirection to each other. Mere friction contact is sufficient if greatenough to prevent any significant relative movement between the twosurfaces.

Vulcanized elastomers which can be used in the non-rigid portion includeconventional tread compounds. Elastomers which can be used includevulcanized polymers having a modulus of 5 to 16 (preferably 12 to 16)meganewtons, an elongation of 400 to 700 (preferably 400 to 500)percent, tensile of 14 to 30 (preferably 20 to 30) meganewtons, a ShoreA hardness of 50 to 90 (preferably 60 to 70) and a resiliency, asmeasured by Goodyear Heally hot (100° C.) rebound, of at least 30percent, preferably at least 60 percent and most preferably at least 70percent. Modulus, elongation and tensile are measured by ASTM D 412.Shore A measurements are made according to ASTM D 2240. Goodyear Heallyrebound is measured by ASTM D 1054.

Although not limited thereto, the following rubber composition can beused in the non-rigid portion after vulcanization thereof, for examplefor 25 minutes at 150° C.

    ______________________________________                                        Ingredients       Parts by Weight                                             ______________________________________                                        Natural Rubber    100                                                         HAF Black         50                                                          Processing Oil    10                                                          Amorphous Silica  20                                                          N--t-butyl-2-     1.5                                                         benzothiazylsulfenamide                                                       Waxes             1.0                                                         Antioxidant       1.5                                                         Antiozonant       1.5                                                         Zinc Oxide         3                                                          Sulfur             2                                                          ______________________________________                                    

A conventional manner of mounting this multi-piece device into a tire isdescribed as follows. One piece (for purposes of this illustration atwo-piece device will be considered) is placed inside the tire with thenon-rigid portion facing the inside surface of the tire beneath thetread. The second piece is placed within the tire and then adhered orfastened at each of its ends to each of the ends of the other half ofthe device.

This device is designed to be used only with a multi-piece rim, forexample a two-piece rim that can simply be bolted together or amulti-piece rim using a removeable flange or flanges, an O ring and lockring.

The run flat device is mounted in such a fashion that it preferably willnot rotate circumferentially around the rim when the vehicle is inmotion. It can either be permanently affixed or loosely affixed, forexample, mounting a radial support between two stoppers which arepermanently affixed to the surface of the rim. The latter positioningwould permit only slight circumferential movement. While lateralmovement would occur in the latter situation, this is normally not aproblem.

Conventional lubricants or coolants normally used with other run flatdevices, such as gels, should be used with the present device tolubricate the interface between the radially outer surface of the outerring and the inner surface of the tire beneath the tread.

FIG. 1 is a perspective view of a device 1 within the scope of thepresent invention. The two halves of the device, 2 and 2', are fastenedat points A and B. The inner rigid ring 4 is surrounded by the non-rigidring 5.

FIG. 2 illustrates, in cross-sectional view, the device 1 mounted withina tire 16 on a three-piece rim 9. The non-rigid portion 5 of the deviceis attached to the rigid portion 4 of the device at the topside of therigid portion 4 by a conventional rubber/metal adhesive. The rigidportion of the device is comprised of two lateral sides 3,3' and atopside 6 which are integrally bound together as a unit construction. Aradial support 7 is also illustrated. When the tire collapses, the outersurface 8 of the non-rigid portion of the device comes in contact withthe inner surface 17 of the tire. It should be noted that this device isused only in tubeless pneumatic tires. The pneumatic tires, however, canbe of either radial or bias construction or cast tires for any type ofvehicle whether passenger, motorcycle, truck or off-the-road, includingmilitary vehicles.

The rigid portion of the device is positioned on the base 10 of thethree-piece rim 9, through the radial support, the lower edge of theradial support being positioned between two stops 8 and 8' (FIG. 3).

After the device is positioned inside the tire, the rim base 10 isinserted through the bead opening of the tire until its permanent flange19 rests near the bead of the tire. The tire is then positioned to shiftthe device toward the permanent flange side so as to permit the moveableflange 18 to be positioned axially toward the center line to expose thegroove in the base, in which the O-ring 11 is to be snapped. The O-ring11 is then positioned and the lock ring 12 then placed in the outergroove of the base. By using a cap screw 15, the lock plate 14 ispositioned against the outer part of the flange and the tire inflated.

The rigid portion 4 of the device can act as a non-positive bead spacer.Should the tire lose pressure and the beads tend to move away from theflange thereby creating the possibility of their demounting from thetire, it will first come in contact with one of the lateral sides of therigid portion of the device thereby preventing the dismounting.

In one embodiment the height of the rigid section of the device is 20 to80 percent of the height of the device.

The device can also be used as a positive or non-positive bead spacerwith a 2-piece rim. With other multi-piece rims such as 3-piece and5-piece rims, the device can be used as a non-positive bead spacer. Asguidelines, but not limitations, the width of the run flat device nearits base should be approximately 0.75 to 1.0 inch less than the rimwidth minus two times the tire bead width for 3-piece rims and should beapproximately 1.5 to 2 inches less than the rim width minus two timesthe tire bead width for 5-piece rim assemblies.

This is necessary to permit the transverse positioning of the moveableflange 18, for example, for insertion of the O-ring 11 and lock ring 13.

FIG. 3 is an enlarged side view of a portion of a device within thescope of the present invention. The non-rigid section 5 is positioned ontop of the rigid section 4. The rigid section 4 has a radial support 7which is positioned between two stops 8,8' welded to the rim base 10.Two ends of the two halves of the device are shown as fastened by a capscrew 13.

When a rim having a moveable flange is used, the device should bedesigned to permit the moveable flange to move without interference fromthe device when the device and tire are being mounted and the rimassembled.

While fabric reinforcement can be used as reinforcement in the non-rigidportion of the device, e.g., to prevent growth due to centrifugal force,its use is not necessary.

In one embodiment of the present invention, the outer ring is aone-piece vulcanized elastomeric band which can be stretched around theouter perimeter of the multi-piece inner ring.

Absolute measurements of resiliency herein are measured by GoodyearHeally hot (100° C.) rebound (ASTM D 1054).

When the outer ring is comprised of vulcanized elastomer, it ispreferably non-porous.

The inside diameter of the device is approximately equal to the nominalrim diameter of the rim on which it is to be mounted.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

What is claimed is:
 1. An assembly of a multi-piece rim, a tire, and arun flat device comprising:(a) a multi-piece rim comprising an annularrim base having a flange extending radially outwardly from one axial endand a pair of circumferentially extending grooves in said rim base nearits other axial end, a movable flange slideably mounted around said rimbase, an O-ring having a portion of its mass disposed within the axiallyinnermost groove of said pair of circumferentially extending grooves insaid rim base, said O-ring being compressedly secured in place betweenthe rim base and the movable flange, and a lock ring having a portion ofits mass disposed in the axially outermost groove of said pair ofcircumferentially extending grooves in said rim base, said lock ringhaving at least one surface that is contiguous with said movable flange;(b) a tubeless pneumatic tire mounted upon said rim, said tire having apair of bead portions with one bead portion disposed adjacent to theflange of said rim base and the other bead portion adjacent to saidmovable flange; and (c) an annular ring-shaped run flat devicecomprising a rigid radially inner ring and a resilient radially outerring, said rings comprising a plurality of arcuate sections, eachsection comprising a radially inner rigid portion having a squaredhorseshoe-shaped cross section and containing radial reinforcements thatare adjacent to the rim base with the open side of said horseshoe-shapefacing radially inwardly, the radially inner extremities of each rigidportion being positioned near said rim base but axially spaced apartfrom the bead portions of said tire, each arcuate section furthercomprising a radially outer resilient portion having a radially innersurface fastened to a radially outer surface of said rigid portion, theradially inner surface of said resilient portion having the same widthas the radially outer surface of said rigid portion, and said run flatdevice having a height that is 25 to 55 percent of the tire sectionheight while the height of the rigid inner ring is 20 to 80 percent ofthe height of the run flat device.
 2. An assembly according to claim 1wherein said rim further comprises a plurality of circumferentiallyspaced apart stops extending radially outwardly from said rim base, oneof the radial reinforcements of said run flat device being disposedbetween said stops to restrict circumferential movement of the run flatdevice with respect to said rim.
 3. An assembly according to claim 2wherein said radial reinforcements further comprise a hexagon in crosssection, having an upper half being substantially rectangular inconforming to the squared horseshoe-shaped cross section of said innerrigid portion and a lower half being substantially trapezoidal, whereinthe radially inner extremities of said lower half are smaller than theradially out extremities of the squared horseshoe-shaped inner rigidportion.
 4. An assembly according to claim 3 wherein said radialreinforcements are adjacent to the rim base and loosely affixed theretoand capable of slideable axial movement.
 5. An assembly according toclaim 4 wherein said acruate sections are joined to one another by afastening means releasably connecting the radial reinforcements of oneacruate section to the radial reinforcements of an adjoining arcuatesection.